Some types of processing machines that irradiate a freely-selected position of a workpiece with a laser beam displace an optical axis of the laser beam. As a concrete measure to change a direction of the optical axis, a combination of a galvano scanner and a condensing lens is often employed (refer to, for example, the following patent documents).
In a scan with the optical axis of the laser beam being displaced, errors in a plane coordinate system are caused due to reasons including a rotational positioning error of a mirror of the galvano scanner, optical distortion of the condensing lens, and the like. It is necessary to remove such errors in advance before performing laser processing.
Previously, a test piece is subjected to the laser processing for a test pattern, and thereafter, an error between the test pattern and an actually-formed pattern is measured by examining the test pattern by a microscope, and a correction amount to reduce the error is added to an instruction value to the galvano scanner and the like.
However, it is very time consuming to examine the pattern formed on the test piece using the microscope, and it is also necessary to provide the microscope with high precision at a workplace since such correction operation is always performed in adjusting the processing machine at the time of assembly and delivery. Moreover, the correction operation is also required at the time of optically adjusting a laser oscillator, exchanging or changing a focal point of the condensing lens, which are troublesome.